In most chess tournament games, each player faces essentially two opposing forces -- his opponent and time. Time plays a critical role in the conduct of the game since it is usually desired to conclude any contest within a realistic period. It is well recognized that time is a major factor in the game of chess, and several variations of the game have been evolved, placing critical priorities on this factor.
One style of chess in which time is of no great significance is postal chess, in which moves are communicated between players through the mail or similar slow channels. The chess clock has no place in this environment. It usually assumes its primary role when used by a pair of players who face each other over a single chess set, in a singular location, ready to play to a checkmate.
The clock thus assumes two major functions. It provides an equal (unless otherwise mutually agreed upon) period of thinking time to each player, and it also restricts the thinking time to a manageable length. This second criteria is of real importance in a tournament environment, where the total length of time available for the conduct of the affair is limited to several days, such as a weekend.
The game of chess is typically played between two opponents (white and black) who make alternate moves in turn until one of the following conditions occurs:
1. One player checkmates the other (or accepts resignation).
2. A draw is agreed upon or is forced.
3. One player runs out of time. Condition "3" is, of course, applicable only in the event that a time limit game is being played.
The general class of chess games in which time plays a significant role may be divided into three distinct categories. The following is a description of each category.
1. Tournament style game. Although tournaments are arranged for all three categories, this game is by far the most commonly played in competition meets. The time portioned each player is divided into periods. The initial (or primary) period is typically about 2 hours long. In these 2 hours, the player is expected to perform a given number of moves (typically about forty). Thus, if each player used the maximum amount of time allowed during the primary period, the real time elapsed would be close to 4 hours. If one of the players runs out of his allotted time before completing the required number of moves, he loses automatically regardless of the board situation. Once a player has performed all his required moves within the primary period, he is allotted additional time (the secondary period) to perform an additional number of moves to be played out in an additional hour.
By completing the primary period's required number of moves, any time left over is added to each player's secondary period. Thus, in the aforementioned example, if white completes his fortieth move in exactly one hour, his secondary period is increased by his unused primary period hour. This process is repeated until a final resolution has been achieved. It is important to note that each player's thinking time is measured separately, thus a player consumes no time while it is his opponent's turn to play.
The typical tournament style game lasts approximately 4 hours, and it is quite common to find players under severe time pressure toward the end of their primary time period, having to complete several critical moves within a small number of minutes.
2. The short game. This game style is in reality only a subset of the standard tournament game. Time is afforded a higher premium, and its relevance to the game becomes almost as important as the opposing player. Each side is allotted a single time period, typically 5-10 minutes, during which it can make an unlimited number of moves, but must also conclude the game naturally (checkmate or draw). Since there is no secondary period, the game also ends when any of the players runs out of time, regardless of board position. In this game style, it is not unusual to find a player in a hopeless board position, hanging on to the game in anticipation of seeing his opponent running his clock out. A common occurrence in this game is seeing both players exhaust their allotted few minutes, and the winner undetermined, as a consequence of their own intense concentration. 3. The seconds game. This game is the fastest moving form of chess. Each player is allowed a set number of seconds, e.g., 10 seconds, to think between any two moves, for an unlimited number of moves. Time is of extreme importance since a player must move within 10 seconds of his opponent's last move, or lose regardless of board position. It is customary to allow each player a couple of seconds grace at the conclusion of his think period, however, a prior art mechanism does not exist that would automatically end the game when a player really overshoots his allotted seconds.